Railroad car handling and classification apparatus

ABSTRACT

A bridge movable in a pit transversely with respect to a plurality of parallel car receiving and classification tracks in a railroad yard is provided with a railroad track thereon extending parallel to the yard tracks and with a self-contained endless conveyor operable in opposite directions to pull cars onto the bridge and to push cars off of the bridge from and to receiving, classification or assembly tracks on either side of the bridge pit. A pair of oppositely directed coupling elements on the conveyor at such elevations and locations as to be engagable with standard, impact connection couplings on the opposite ends of a railroad car are used sequentially to engage one end of a car and to pull it onto the bridge from one direction and to engage the opposite end of the car and push it off of the bridge onto a classification or assembly track in the opposite direction; or, the car may be shuttled back to the same side of the pit from whence it came after the bridge is moved to a new track location, by simply reversing the direction of the coupling motion.

United States Patent 1191 Sternad Sept. 4, 1973 RAILROAD CAR HANDLING AND CLASSIFICATION APPARATUS Primary Examiner-Gerald M. Forlenza Assistant Examiner-D. W. Keen Attorney-Herman H. Bains, Malcolm L. Moore et :11.

[57] ABSTRACT A bridge movable in a pit transversely with respect to a plurality of parallel car receiving and classification tracks in a railroad yard is provided with a railroad track thereon extending parallel to the yard tracks and [52] US. Cl. 104/48, 104/172 C with a self-contained endless conveyor operable in op- [51] Int. Cl. B61] l/lO o ite directions to pull cars onto the bridge and to Field f Search push cars off of the bridge from and to receiving, classi- 2 /1 26 fication or assembly tracks on either side of the bridge 26 A, 147, 148, 149, 151, 162, 172 A, 172 B, pit. A pair of oppositely directed coupling elements on 172 C the conveyor at such elevations and locations as to be engagable with standard, impact connection couplings References Cited on the opposite ends of a railroad car are used sequen- UNITED STATES PATENTS tially to engage one end of a car and to pull it onto the 3,169,490 2/1965 Saxonmeyer 104/162 bridge fmm directi?" and to engage the 1,323,307 10/193] end of the car and push 1t off of the budge onto a classi- 3,l54,023 10/1964 fication or assembly track in the opposite direction; or, 3,212,454 10/1965 the car may be shuttled back to the same side of the pit 1 H 1 from whence it came after the bridge is moved to a new MIICI'ICII track location reversing the direction of the coupling motion.

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William A.8ternad Q BY PATENIED SE? 4 I975 SHEET ll- UF 6 IN VENTOR.

William A. Sternad TTOE/VEVS msmansu 4191a 3.756159 sum 5 BF 6 I N VEN TOR.

William/L. Stern ad PATENTEDSEP 4 mm 33756159 sum 6 BF 6 IN VENTOR. William A. Sternad RAILROAD CAR HANDLING AND CLASSIFICATION APPARATUS BACKGROUND OF THE INVENTION In accordance with the present state of the art relating to railroad car classification systems, the most recently developed means for separating and classifying freight cars in a yard is the so-called hump yard system. In accordance with this procedure, switch engines are used to move railroad cars over a hump, after which the freight car is disengaged from the engine and allowed to roll freely on a classification or storage track where it is subsequently stopped and brought under control by a retarder device of some kind. See for example, U.S. Pat. No. 3,154,023 issued to Karlet et a]. wherein the traditional hump yard with its retarders and impellers for regulating the free movement of freight cars is disclosed. Such systems suffer from the inherent disadvantage of the requirement of expensive and complex retarder and impeller devices and associated controls, as well as from the problem of damage to freight cars and their cargos resulting from the impact of free moving cars with each other.

Switching and classification systems utilizing socalled transfer table or bridge devices located between a plurality of parallel tracks and movable transversely thereof have also been proposed as means for shifting the railroad cars onto classification and storage tracks, the transversely movable table or bridge having tracks thereon for receivingrailroad cars. In accordance with such systems, the movable bridge is normally disposed in a pit, and is shifted by power means in a direction transversely of a plurality of classification tracks into alignment with a particular track where it receives a car. The bridge is then moved in the pit to a position of alignment with a second track onto which the car is moved for storage. Such bridge or transfer table system as are presently known suffer from several disadvantages, and to the best of my knowledge, have never been satisfactorily developed to the point where they can perform the high volume car shifting and classification operation required in large freight yards, as is necessary to replace the conventional hump yard system. One of the primary problems associated with presently known transfer table and bridge systems is that they do not have car conveyor or moving means on the bridge capable of moving cars onto and off of the transfer table or bridge with sufficient power and control to avoid the necessary and undesirable throwing or kicking-off of the cars from the bridge with free, uncontrolled movement, thereby requiring the use of retarders and stopping devices on the receiving, classification tracks.See, for example, US Pat. No. 1,366,292 issued to Smith. Where conveyor devices have been conceived and proposed for moving cars onto and off of transfer bridges or tables under complete control, the

conveyor devices have not been devised in such a way the transfer bridge shown in the Mitchell patent may be modified to remove cars on the opposite side of the bridge from that on which they are received, the conveyor mechanism is not readily adaptable and usable on any given switching operation for depositing a car on a siding or classification track on either side of the bridge.

Having in mind the foregoing difficulties and shortcomings associated with presently known railroad car shifting and classification systems used in marshalling yards, I have devised an improved transfer bridge system which is provided with a self-contained, power driven conveyor having couplings so constructed and arranged thereon so as to be capable of pulling cars onto the bridge from either side of the bridge pit, and for pushing cars off of the bridge onto classification or assembly tracks on either side of the bridge pit, in the course of any given switching operation. The conveyor and coupling means on the bridge accomplish the car classification process in a static mode as opposed to the conventional dynamic mode utilized in hump yards, with each car being maintained under complete control of the conveyor on the bridge until its movement onto or off of the bridge has been completed, in accordance with my improved car conveyor and associated coupling means on the bridge. The need for retarders, impellers, and associated controls normally re quired in hump yards, and the attendant damage to freight cars and their cargos by impact resulting from free movement of cars are thus eliminated.

BRIEF SUMMARY OF THE INVENTION This invention is directed to an improved transfer bridge type of railroad car classification apparatus which is particularly characterized by a car conveyor and attached coupling means carried on the bridge and movable on the bridge by power drive means in opposite directions parallel to a plurality of classification and assembly tracks traversed by the bridge so as to be capable of conveying cars onto the bridge from either side thereof and moving a car off of the bridge onto a predetermined classification or assembly track, with all car shifting movement being under complete control of the conveyor until a car has been brought to a stop on the bridge, or on a classification or assembly track in alignement with a car track on the bridge. These basic objectives are realized by utilizing an endless conveyor rotatably mounted on the bridge and carrying two, oppositely directed coupling elements constructed and arranged to be received in positive, locking engagement with complementary coupling means on the opposite ends of a railroad car, the coupling elements being of such a shape and extent, and so mounted on the car conveyor on the bridge as to be movable therewith to a location wherein one or the other of the coupling elements is immediately adjacent to one or the other of the opposed side edges of the pit within which the bridge is movably mounted for traversing movement with respect to a plurality of parallel classification and assembly tracks. By virtue of this conveyor and coupling arrangement, one or the other of the oppositely directed coupling elements may be utilized for releasing or picking up a railraod car on one of the plurality of incoming, classification, or assembly tracks on either side of the bridge pit by engagement with a complementary coupling on the end of a railroad car. One of the coupling elements may be utilized to pull a car onto the bridge from an incoming track, and by disconnecting this coupling element, and revolving the endless conveyor to bring the second, oppositely directed coupling element into engagement with the coupling on the opposite end of the railroad car, the conveyor can be utilized to push the car off of the bridge onto a classification or assembly track on the opposite side of the bridge from which the car was received.

The power means for driving the car conveyor on the bridge has sufficient power to pull a car or cars onto the bridge, and to push a car off of the bridge without the use of supplemental, external power of any kind. Thus, with the coupling means on the car conveyor of the bridge being positively engaged with a car during the entire course of a car shifting movement, the conveyor, its coupling means and the attendant power means for the conveyor completely replace the conventional switch engine with comparable flexibility for moving trains and cars onto and off of the bridge in opposite directions. The cost of switch engines, and the undesirable noise and exhaust gases associated with the use of switch engines are thus elimintated. Such ecological benefits directly accrue from my railroad car switching system and are an important advantage of it. Not only does the elimination of Diesel switch engines avoid the noise and smoke pollution attendant to their operation, but also, since humping is eliminated the crashing noises associated with this operation are also precluded. Moreover, power is consumed only when switching work is being done, in contrast with switch engines, whose Diesel engines run constantly even though not in use and continuously emit polluting smoke.

As a particularly advantageous feature of my improved transfer bridge unit, the coupling elements on the car conveyor carried on the bridge are of the impact engagement type constructed and arranged on the car conveyor to mate and be received in locking engagement with the oppositely directed couplings on the opposite ends of a railroad car normally used for coupling one car to another or to a switch engine. The coupling elements on the car conveyor are preferably parts of a single coupling assembly with two coupling elements oriented in opposite directions and affixed to the car conveyor on the bridge in such a manner that the coupling elements project upwardly above the railroad car track provided on the bridge to a level even with the standard couplings located on opposite ends of a railroad car. The conveyor may be revolved in order to bring one of the coupling elements into alignment and engagement with a coupling on the end ofa railroad car on a classification track with which the bridge track is aligned.

A further beneficial aspect of my invention resides in the arrangement of the car conveyor on the bridge in a horizontal plane with the opposite ends of the endless conveyor looped around rotary guides at opposite ends of the bridge, the rotary guides having vertical axes. This arrangement permits the extended coupling elements to be rotated with the conveyor through a complete 360 path as required for engaging the opposite ends of a railroad car without being obstructed by the opposite sides of the pit across which the movable bridge extends, as would be the case with an endless conveyor revolving in a vertical plane. The conveyor is looped around one of the track rails of the car track on the bridge, and this track rail is provided with displaceable track segments at its opposite ends, either one of which may be withdrawn to a position providing a clearance space at one end or the other of the bridge track rail to permit the upwardly extending coupling elements to be carried around the ends of the track rails as required for a coupling position, or for placing the coupling elements outside of the bridge track where they will not interfere with the movement of a car across the track from one side of the bridge pit to the other.

These and other objects and advantages of my invention will become readily apparent as the following description is read in conjunction with the accompanying drawings wherein like reference numerals have been used to identify like elements throughout the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of the railroad car handling and classification apparatus of this invention;

FIG. 2 is a vertical, section view of one end of the transfer bridge taken along lines 22 of FIG. 1;

FIG. 3 is a top, plan view of one end of the transfer bridge and the car conveyor on the bridge, on an enlarged scale;

FIG. 4 is an end, elevation view of the bridge and conveyor structure of FIG. 3;

FIG. 5 is a top, plan view of one end of the bridge and conveyor structure, similar to FIG. 3 and showing the retractable track segment at one end of the bridge track fully extended;

FIG. 6 is a vertical section view taken along lines 6-6 of FIG. 5;

FIG. 7 is a vertical, section view of one end of the bridge unit taken along lines 77 of FIG. 1;

FIG. 8 is a vertical, section view of the bridge unit taken along lines 8-8 of FIG. 7;

FIG. 9 is a vertical, elevation view taken along lines 9-9 of FIG. 1 and showing the power drive assembly for the chains utilized to move the bridge back and forth in the bridge pit; and

FIG. 10 is a vertical, section view of the power drive assembly for the bridge chains taken along lines l0l0 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIGS. 1 and 7, I have illustrated my railroad car handling system in a switch yard or classification yard, a portion of which is shown in FIG. 1, and which includes a through track 1. Adjacent to track 1 are a plurality of parallel, car receiving, classification, or assembly tracks 20 through 22 which terminate at their inner ends at one side edge of a pit 4. Opposite tracks 2e 2f, and in alignment therewith are a second group of car receiving, classification, or assembly tracks 6a- 6e which terminate at their inner ends at the opposite side edge of pit 4. Pit 4 is defined by upright side walls 4b and opposed, upright end walls 4a. Railroad cars to be classified and stored on one of the tracks 2a 2e or 6a 6e are initially moved on to one of the receiving tracks 2a or 611 from through track I by conventional switching means, not shown. Several railroad cars 8 are shown in position on the various tracks. I contemplate that in utilizing my railroad car handling and classification apparatus, any of the tracks, 2 and 6 might serve as incoming, receiving tracks for cars to be classified, and that any of these tracks could serve as an outgoing track on which outbound trains are made up or assembled with cars in a predetermined order prior to moving the completed, new trains out of the yard. Each of the railroad cars 8 is provided with standard, impact couplings 10a and 10b at their opposite ends, these couplings being standard, Association of American Railroad couplings.

Movably positioned in pit 4 for lateral shifting in a direction transverse to classification and receiving tracks 2a 2e and 6a 6e is a bridge 12. As is clearly indicated in the plan view of FIG. 1, bridge 12 spans substantially the entire length of pit 4 in a direction parallel to the receiving and classification tracks, with sufficient clearance space at the opposite ends of bridge 12 adjacent pit side walls 4b to permit the lateral movement of the bridge within the pit. This clearance space will normally be held to a very close tolerance on the order of 1 to 2 inches to permit cars 8 to be moved on and off of bridge 12 from the receiving, classification and assembly tracks 2a 2e and 6a 6e. For this purpose, bridge 12 is provided with a track 14 extending over substantially its entire length in a direction parallel to the receiving and classification tracks, the rails 14a and 14b defining track 14 being at the same elevation as tracks 2a 2e and 6a 6e, as is shown in FIGS. 2 and 7. Bridge 12 is movable back and forth within pit 4 to convey cars received thereon to a position of alignment with one of the classification or assembly tracks 2b 2e or 6b 6e, to permit cars to be moved off of bridge 12 onto one of these classification or assembly tracks for storage or outgoing train make-up. To this end, a plurality of parallel tracks l6, l7, l8 and 19 are installed on the floor of pit 4 in a direction transverse to the receiving classification and assembly tracks 2a 2e and 6a 6e. As may be noted most clearly by reference to FIGS. 7 and 8, bridge 4 is supported on a plurality of wheeled carriages 20 and 21 which run back and forth on tracks 16 19. There are actually eight such carriages for the bridge, two of which are located at spaced apart locations along the length of the bridge coinciding with the location of tracks 16, 17, 18 and 19. Pit 4 is preferably provided with a concrete floor 22 within which steel runners 24 are imbeded to provide support under the rails of tracks 16 19. A plurality of reinforcing rods 26 are used in concrete floor 22 for conventional strengthening and reinforcing purposes.

I contemplate that various power means drivingly associated with bridge 12 may be utilized to move it back and forth on tracks 16 19. One drive means for the bridge 12 utilizing chains 28 and 30 is illustrated in FIGS. 7, 9 and 10. The two chains 28 and 30 are continuous chains extending in loops as illustrated in FIG. 1, and slidably supported on a plurality of slide runners 32, 33 and 34 extending transversely of pit 4 in a direction parallel to tracks 16 19. The end sections of chains 28 and 30 extending in a direction parallel to bridge 12 are supported on end slides 35, 36 and 35a 36a. Chains 28 and 30 are each guided around four corner sprockets designated by reference numerals 38 and 39 respectively, the drive sprockets being designated 38a and 39a. The outer lengths of each of the drive chains 28 and 30 terminate at opposite sides of bridge 12, and are coupled thereto by upright connecting pins 40, 41 and 42, 43 respectively, as is indicated in FIGS. 1 and 7. These pins extend through the base of the bridge frame structure, as is illustrated with re spect to connecting pin 43 in FIG. 7.

In FIGS. 9 and 10, I have illustrated the power drive means for driving chains 28 and 30. Although various drive arrangements may be utilized, I have found it practical and convenient to utilize a hydraulic drive motor 44 having a drive shaft 45 connected to drive sprocket 38a for chain 28. Drive shaft 44 is rotatably supported at spaced points along its length in bearings 46 47 which are attached to a wall bracket assembly 48, from which hydraulic motor 44 is also supported by an overhead bracket plate 49. The entire bracket assembly 48 is mounted on end wall 4a of pit 4. A pinion gear 50 on drive shaft 45 is in driving engagement with gear 52 mounted on a second drive shaft 54, serving to transmit rotary power to drive sprocket 39a for drive chain 30. Shaft 54 is rotatably supported in bearings 55 and 56.

The frame structure and support carriage arrangement for bridge 12 may be best understood by reference to FIGS. 7 and 8. The basic, structural components of the bridge assembly are a pair of elongated I- beams 58 and 60 which extend the length of bridge 12 directly under track rails 14a and 14b to provide good support for railroad cars 8 being conveyed on the bridge. If it is deemed desireable, a section of track rails 14a and 14b can be supported through intermediate force load cells (not shown) so that car weight can be ascertained when cars pass over this .live section. A plurality of reinforcing, gusset plates 62 extend between I-beams 58 and 60 at spaced apart points along their length. A plurality of larger, upright gusset plates 64 and 65 are attached to I-beams 58 and 60 and extend outwardly therefrom to support an operator deck or platform 66 running along the front and back of the bridge on opposite sides of bridge track 14. A guard rail 68 shown in FIG. 8 preferably extends along the back edge of operator deck 66, operator stations 67 and 670 at opposite ends of the bridge being shown in FIG. 1. I-beams 58and 60 are supported on top of wheeled carriages 20 and 21 by means of elongated beams 70 resting on cross braces 72 which extend transversely of the carriages 20, 21 and rest on carriage chassis beams 74.

For the purpose of moving railroad cars 8 onto and off of bridge 12, an endless conveyor is utilized. This conveyor preferably takes the form of an endless chain 76 looped in a horizontal plane about large sprockets 78 and 79 rotatably supportedon vertical axes at opposite ends of bridge 12. The rotational axes for sprockets 78 and 79 are defined by the drive spindles 80 and 81 for these sprockets. For reasons hereinafter explained, car conveyor chain 76 is arranged in a continuous loop extending around track rail 14a of bridge track 14, as appears most clearly in FIGS. 1, 3 and 4, with chain 76 extending over the entire length of bridge 12 and its opposed, looped ends terminating immediately adjacent the opposite ends of the bridge. The location, drive and support arrangement for car conveyor chain 76 is most clearly illustrated in FIGS. 2, 3, 4 and 8. Chain 76 is a multiple link chain having vertically extending segments slidably supported on runners 82 and 83 extending lengthwise along bridge 12. Sprockets 78 and 79 are likewise supported on slide bearings 84, all of these slide runners and bearings preferably being wood impregnated with a lubricant. As may be noted with respect to FIGS. 3 and 8, upper, operator deck 66 is vertically offset along the front, or right edge of bridge 12 as viewed in FIG. 8, to accommodate vertically extending conveyor chain 76, the lower, forward portion of deck 66 being designated by reference numeral 66a. Rotary power is supplied to sprocket drive spindles 80 and 81 by means of two pairs of hydraulic motors 86 and 87 located at opposite ends of bridge 12. There are thus a total of four hydraulic drive motors for conveyor chain 76, each of which is sized to develop 400 horsepower. These hydraulic motors are preferably free wheeling so that any number of them may be selectively utilized in combination, depending upon the number of cars and/or the size of a train being pulled by conveyor chain 76. Three of the hydraulic motors 86, 87, developing a total of 1,200 horsepower, will produce power equal to that of an ordinary switch engine, thus leaving the fourth hydraulic motor as a spare. An identical drive arrangement using two hydraulic motors is utilized at both ends of bridge 12 to drive chain sprockets 78 and 79. In FIG. 4, I have shown the hydraulic motor drive assembly for sprocket 78 at the left end of bridge 12, as viewed in FIG. 1. Each of the hydraulic motors 86 and 87 includes an upper, stationary housing 8 8 which is attached to a horizontally extending bracket plate 89 of the bridge structure by a plurality of fasteners 90. Hydraulic motor housings 88 serve as upper bearings for rotors 92 of the hydraulic motors which are drivingly coupled to pinions 94 and 95 by means of a plurality of threaded fasteners 96 extending therebetween. Drive pinions 94 and 95 are arranged in driving engagement with the teeth of a driven gear 98 mounted on spindle 80 for spricket 78. Pinions 94 and 95. are mounted on shafts which are rotatably supported at their lower ends in bearings 100affixed to U-beams 102 extending transversely of the structure of bridge 12. Likewise, drive spindle 80 for sprocket 78 is rotatably supported in bearings 104. It is to be noted, with respect to FIG. 7, that I-beam 60 is cut away at its forward end 60a, at both ends of bridge 12 in order to accommodate chain sprockets 78 and 79, and their drive assemblies.

Each of the hydraulic drive motors 86, 87 for spindles 78 and 79 is supplied with hydraulic fluid from a separate pump driven by an electric motor, one of such pumps and motor combinations being illustrated at 106 and 107 in FIG. 7. Fluid supply and return lines 108 and 109 are shown connected between pump 106 and hydraulic drive motor 87. There is a separate switch gear from which electric power is supplied to each of the electric drive motors 107, two of such switch gear assemblies being shown at 110 and 111 in FIG. 7. Each switch gear unit includes a manual disconnect switch 112 and a magnetic starter 113. Power is supplied to the switch gear units 110, 111, etc., from a main power line running along one side of pit 4 (not shown), from which power is conducted to bridge 12 and the switch gear units by means of a trolley type of electrical pick up device. The motor, pump and switch gear apparatus for driving hydraulic motors 86 and 87 may be mounted on an equipment deck supported from main I-beams 58 and 60 on opposite sides of these beams.

Attached to car conveyor chain 76 for use in engaging railroad cars 8 is at least one coupling assembly 114. Preferably, as is illustrated in FIG. 1, two of these coupling assemblies 114 and 115 are utilized for a reason hereinafter explained. These two coupling assemblies are of identical construction, and one of the assemblies is illustrated in detail in FIG. 2. As may be noted with respect to FIG. 2, each of the coupling assemblies 114, 115 is comprised of an upright extension 116 of conveyor chain 76. Attached to opposite side of chain extension 116 are a pair of gusset plates 117 and 118 which lend strength and rigidity to chain extension 116, and which serve as attachment means for coupling elements. Preferably, for reasons set forth below, each coupling assembly includes a pair of oppositely directed and oriented coupling elements 120 and 121. As appears most clearly in the plan view of FIG. 1, coupling elements 120 and 121 of each coupling assembly are oppositely oriented in such a way that their coupling receiving openings face in opposite directions. By virtue of this coupling assembly arrangement, coupling elements 120 and 121 can be selectively utilized to engage the oppositely directed coupling elements 10a and 10b on the opposite ends of railroad cars 8. To this end, coupling elements 120 and 121 are standard, impact couplings identical in structure to railroad car couplings 10a and 10b. Thus, coupling elements 120 and 121 may be engaged in positive, locking engagement with car couplings 10a and 10b to maintain positive control over the railroad cars as they are being pulled onto and off of bridge 12. In FIGS. 1 and 2 the use of oppositely directed coupling elements 120 and 121 of coupling assembly 115 to engage oppositely directed couplings 10a and 10b on opposite ends of railroad cars is illustrated. It will be appreciated that car conveyor chain 76 can be revolved in order to move one or the other of coupling assemblies 114 and 115 into position between track rails 14a and 14b of bridge track 14 for alignment with the coupling on one end of a railroad car to be conveyed onto or off of bridge 12. The height of chain extension 116 of the coupling assemblies 1 l4 and 115 is such that coupling lements 120 and 121 will be disposed at an elevation above bridge track 14 coinciding with the elevation of couplings 10a and 10b on cars 8. The connection of coupling elements 120 or 121 with a car coupling 10a or 10b is simply accomplished by revolving conveyor chain 76 in the appropriate direction to force one of the coupling elements 120 or 121 into impact engagement with a complementary coupling 10a or 10b on a car 8. Where two coupling assemblies 114 and 115 are used, they are located less than apart, so that they can both be moved with chain 76 to the outside of bridge track 14 in a position where they will not interfere with the free movement of railroad cars across bridge 12, when cars are to be propelled by a switch engine, or other means from a receiving track directly onto the aligned outgoing track 6, over bridge 12. In such an event, both of the coupling assemblies 114 and 115 would have to be on the side of bridge track 14 where coupling assembly 114 is shown in FIG. 1. Drive sprockets 78 and 79 are located at such elevations that the top of these sprockets, and the top of conveyor chain 76 is disposed below track rails 14a and 14b of bridge track 14 to avoid interference with the passage of railroad cars over bridge 12. This height or elevation relationship of sprockets 78 and 79 and chain 76 to bridge track 14 is illustrated in FIGS. 2 and 4.

An important and very advantageous feature of my railroad car handling apparatus resides in the fact that car conveyor chain 76, and coupling assemblies 114 and 115 are so located and arranged that one or the other of the coupling elements 120 or 121 of a particular coupling assembly may be moved to a position immediately adjacent one of the side edges 4b of pit 4. Thus, as is illustrated with respect to coupling lement 120 in FIG. 2, the arrangement of conveyor chain 76 in a horizontally extending loop with the chain revolving about vertical axes, together with the shape and extent of the coupling elements, permits chain 76 to be rotated to a position wherein coupling element 120 is positioned right at the edge 41) of pit 4 for releasing or picking up a railroad car 8 by engagement with its coupling 10b. It will be appreciated that by using hydraulic motors 86 and 87 to revolve conveyor chain 76 in a counterclockwise direction as viewed in FIG. 1, cou pling element 121 can be moved across bridge 12 to a position immediately adjacent the opposite, or left side of pit 4 wherein it can be brought into positive, interlocking engagement with coupling 100 on a railroad car 8 on receiving track 2a.

When desired, reversable car conveyor chain 76 may be driven so as to move coupling assemblies 114 and 115 around the opposite ends of bridge track rail 14a at opposite ends of bridge 12 in order to properly position the coupling assemblies and orient them for engagement with a complementary coupling on a railraod car. Since coupling assemblies 114 and 115 are maintained at the same elevation and in the same horizontal plane at all times by reason of the rotation of conveyor chain 76 about the vertical axes defined by sprocket spindles 80 and 81, coupling elements 120 and 121 will not strike or be obstructed by side walls 4b of bridge pit 4, even though they overhang the side edges of the bridge pit when being revolved around the ends of bridge track rail 14a. However, in order that upwardly projecting chain extension 116 of the coupling assemblies may be rotated past the ends of track rail 14b, there must be a clearance space between the ends of this track rail and the adjacent edge of pit side walls 4b, sufficient to accommodate the width of chain extension 116. Since such a clearance space can not normally be maintained between the ends of bridge track 14, and the adjacent tracks 2e and 6a 62 because this would require too large'a track gap to permit the free and unimpeded rolling movement of cars onto and off of bridge 12, provision is made to create a clearance space at the opposite ends of track rail 14b when it is necessary to revolve one of the coupling assemblies 114 or 115 around the end of this track rail. As may be understood by reference to FIGS. 2 through 6, this is accomplished by providing a displacable, slidably shiftable track segment 140 at each end of track rail 14a in alignment therewith. To permit its sliding, shifting movement in a direction longitudinally of track rail 14a, displacable track segment 14c is attached to a slide plate 122 by a plurality of longitudinally spaced gusset plates 124 welded thereto. Attached to the underside of slide plate 122 are a plurality of bearing discs 126, which may be wood impregnated with a lubricant. Discs 126 are slidably shiftable back and forth across the top of the planar, top face of chain sprockets 78 and 79 at the opposite ends of bridge 12. It is to be understood that the same, retractable track segment as sembly is utilized at both ends of bridge rail 14a, even though this assembly is described herein with reference to the left end of bridge 12 as viewed in FIG. 1. To provide sliding support for plate 122 at its rear end, as well as at its forward end, a supplementary, horizontally extending plate 128, shown most clearly in FIGS. 2, 3 and 6, is positioned inwardly from sprockets 78 and 79, at the same level with the top thereof. Plates 128 are supported on upright members 130 resting on horizontally extending bracket plate 89. It is to be noted that operator deck 66 terminates short of the opposite ends of bridge 12, in the area where the drive sprockets 78 and 79 and their drive assemblies are located, and that support plates 128 are located in the space between sprockets 78, 79 and the end extremities of operator deck 66, as is illustrated in FIG. 3. It will thus be seen that the most inwardly disposed bearing discs 126 of slide plate 122 will slide back and forth over support plate 128. If desired, an air compressor 131 shown in FIG. 7 may be used to supply pressurized air to the underside of bearing discs 126 to provide an air cushion effect.

Normally positioned in line with track rail 14a between the outer end of this rail, and shiftable track segment 140 is a removable track segment 14d, as shown in FIGS. 3 and 5. Track segment 14d is displaceable at right angles to track 140 between guide blocks 132 in order to provide an open space or gap into which track segment 140 may be retracted. For the pur pose of moving displaceable track segments 14c and 14d back and forth as required, I utilize a pair of hydraulic cylinders 134 and 135, the piston of cylinder 134 being connected to slide plate 122, and the piston of cylinder 135 being connected to track segment 14d. In FIG. 5, track segment 14d is shown in place and retractable track segment is shown fully extended in its normal position of use, with hydraulic cylinders 134 and 135 extended. When it is desired to rotate one of the coupling assemblies 114 or 115 around one end of bridge track rail 14a, hydraulic cylinder 135 is first actuated to retract its piston and pull track segment 14d outwardly to the position shown in FIGS. 3 and 6. Then, hydraulic cylinder 134 is actuated to withdraw its piston and to pull slide plate 122, and track segment 14c with it rearwardly to the retracted position shown in FIG. 3, into the gap vacated by track segment 14d. In this manner, a clearance space may be provided at one end of track rail 14a to permit upwardly projecting chain extension 116 of one of the coupling assemblies to be revolved around the end of track rail 14a in either a clockwise or counterclockwise direction. Preferably, I utilize a non-contacting proximity control device, such as a photoelectric cell to automatically actuate hydraulic cylinders 135 and 134 in the desired, aforesaid sequence when one of the coupling assemblies approaches displaceable track segments 140 at either end of bridge 12. Such a control device is illustrated schematically at 136 in FIG. 5. By the use of such a control device, the operators on bridge deck 66 can be relieved of the responsibility of manually operating hydraulic cylinders 134 and 135 to retract rail segment 14c when a coupling assembly 114 or 115 is being pulled around one end of track rail 140 on chain conveyor 76.

Slide plate 122 is provided with a plurality of elongated slots 137 and 138, slots 138 being sized to receive guide pins 140. Larger slot 137 receives the upper end of spindle shaft 80 for sprocket 78. These upright guide members 80, and 140 serve to guide slide plate 122 along a straight path in line with track rail 14a as plate 122 and track segment 14c are extended and retracted by hydraulic cylinder 134.

In operation, one or more railroad cars 8 are positioned on a receiving track such as 2a for separation,

classification and storage on classification tracks 2!) 2e and 6a 6e. Bridge 12 is of sufficient length that it may receive two cars at a time in the manner illustrated in FIG. 1. Three shorter cars could also be accommodated. Also, as noted above, hydraulic motors 86 and 87 for conveyor chain sprockets 78 and 79 generate sufficient horsepower, comparable to that of a switch engine, that chain 76 may be utilized to pull a train of cars onto the bridge 12 with one or two cars then being uncoupled from the rest of the train after they have been pulled onto the bridge. In any event, at least one car is positioned on receiving track 2a with its coupling a extending over the side wall 4b of pit 4 in position to be engaged by one of the coupling assemblies 114 and 1 on conveyor chain 76. With a car so positioned on receiving track 2a, as is illustrated in FIG. 1, conveyor chain 76 is revolved in a counterclockwise direction, as viewed in FIG. 1, in order to bring one of the coupling elements 121 into position between track rails 14a and 14b at the end of bridge 12 adjacent receiving track 2a. It will be noted that coupling element 121 is oriented so as to be received in locking engagement with coupling 10a on the end of car 8 shown on track 2a in FIG. 1. An operator positioned at control station 67 on deck 66 of bridge 12 operates the hydraulic drive motors 86 and 87 to revolve conveyor chain 76 at the desired speed and in the required direction. Coupling element 121 is positively engaged with coupling 10a on car 8 by revolving conveyor chain 76 at a sufficient rate of speed to force coupling element 121 and car coupling 10a together, in the same manner as is accomplished between standard, impact couplings on railroad cars. Conveyor chain 76 is then revolved in the opposite, clockwise direction to pull one or more cars onto bridge 12. In the illustration shown in FIG. 1, coupling assembly 115, and its coupling element 121 are shown engaged with one of two cars 8 which have been pulled onto bridge 12. Also, for illustrative purposes, I have shown in FIG. 1 how the oppositely oriented coupling element 120 could be engaged with a coupling 1011 on a car on track 6a in order to pull a car from track 6a onto bridge 12 from the opposite direction. After one or two cars have been received onto bridge 12, the bridge is moved along rails 16 19, utilizing drive chains 28 and 30 to bring bridge 12 into alignment with a particular classification track onto which the cars from bridge 12 are to be moved for storage and classification. Control station 67a at the opposite end of bridge 12 from station 67 may be provided with the necessary controls for operating drive motor 44 for chains 28 and 30. If the cars on bridge 12 are to be moved onto one of the classification or assembly tracks 2b 2e, the coupling element 115 attached thereto is revolved with chain 76 in a counterclockwise direction to push the cars off of bridge track 14 onto one of the classification or assembly tracks 2b 22. As with the operation of pulling cars onto bridge 12, coupling assembly 115 is maintained in engagement with one of the cars 8 throughout the entire operation of moving the cars off of bridge 12 until the last car is received onto one of the classification or assembly tracks 2b 2e with its coupling 10a overhanging the side wall 4b of pit 4. Then, one of the operators on the bridge deck disengages coupling element 121 from car coupling 10a. Thus, my particular coupling and car conveyor chain arrangement permits cars to be moved onto and off of bridge 12 under complete control at all times, without the necessity of throwing" cars on and off the bridge, with the resultant free motion of cars requiring, as in the prior art, the use of impeller and stop devices to control the motion of freight cars during the classification operations. Also, the damage to cars and their cargos resulting from the impact of moving cars with each other is eliminated.

If the two cars shown on bridge 12 in FIG. 1 are to be received onto one of the classification or assembly tracks 6b 6e on the opposite side of pit 4, then one of the oppositely oriented coupling elements 120 must be engaged with coupling 10b of car 8a on the left end of bridge 12 as viewed in FIG. 1. To accomplish this, coupling element 121 of coupling assembly is disengaged from car 8b on bridge 12, the car conveyor chain 76 is revolved in a clockwise direction in order to bring coupling element of coupling assembly 114 into engagement with coupling 10b on car 8a. By using two, spaced apart coupling assemblies 115 and 114 as shown in FIG. 1, the time required for revolving car conveyor chain 76 to bring one of the oppositely directed coupling elements 120 into engagement with car 8a is minimized. It will be appreciated that only one coupling assembly 115 could be utilized, and that after disengaging this coupling assembly from car 8b, it would be revolved all the way around the opposite end of track rail 14a to bring its coupling element 120 into engagement with coupling 10b on car 8a. After the engagement of one of the coupling elements 120 with coupling 10b on car 8a has been accomplished, chain 76 is again driven in a counterclockwise direction to utilize the coupling assembly to push cars 80 and 8b off of bridge 12 onto one of the classification tracks 61) 6e with which bridge track 14 has been moved into alignment. By using at least one pair of oppositely directed and oriented coupling elements 120 and 121 in the foregoing manner, with an endless conveyor chain arranged as disclosed herein, 1 am able to pull cars onto bridge 12 from one side of pit 4, and push the cars off of bridge 12 onto the opposite side of the pit. Thus, complete flexibility of classification and assembling operation, utilizing such a pair of oppositely directed coupling elements is achieved to permit cars to be pulled onto bridge 12 from either side of pit 4, and then to be pushed off of the bridge onto either the same side of the pit from which they were received, or onto classification tracks on the opposite side of the pit 4.

Also, I contemplate that it is not necessary to have a pair of coupling elements 120 and 121 as part of a unitary coupling assembly. Two oppositely directed coupling elements 120 and 121 could be attached to car conveyor chain 76 at spaced apart locations thereon, and still achieve the above described operating results. With such an arrangement utilizing two, spaced apart single couplings 120 and 121, one of the coupling elements would be used to pull a car onto the bridge, and the other, oppositely oriented coupling element would be utilized to engage the opposite end of the car and push it ofi' of the bridge in the opposite direction, if so required. If only one couplingelement 120 and 121 were utilized on conveyor chain 76, the advantages of maintaining positive control over cars while they are being moved onto and off of the bridge 12 would still be achieved; however, it would then only be possible to pull cars onto and off of bridge 12 from only one side of pit 4b, depending upon the direction in which the coupling element 120 or 121 were oriented.

The use of coupling elements 120, 121 identical to standard, railroad car impact couplings on a conveyor chain 76 driven with power comparable to that of a switch engine, permits my conveyor chain 76 and coupling assemblies 114, 115 to function in all respects like a switch engine, with the same directional flexibility and power. However, the disadvantages of having to utilize several switch engines on the various receiving and classification tracks to move cars onto and off of bridge 12 are eliminated. in particular, the noise and air pollution incidental to the use of switch engines are eliminated. Also, the use of coupling elements 120, 121 of the standard, impact type permits the application of controlled power to cars 8 while they are being moved, in contrast with the use of strike or contact elements of some kind on a conveyor which merely strike against some points on the undercarriage of a railroad car and throw it onto or off of the bridge. With my conveyor chain and coupling arrangement, a railroad car is not released until chain 76 has been stopped, and one of the coupling elements 120 or 121 is disengaged from a railroad car 8.

I also contemplate that many of the advantages of positive, controlled movement of railroad cars onto and off of the bridge, and a certain degree of flexibility of car movement could be achieved by using only one pair of oppositely directed coupling elements 120 and 121 on a unitary coupling assembly, or in closely spaced relation on a conveyor arranged in position between track rails 14a and 14b in such a way that the couplingelements could only be maintained at all times between the rails of the bridge track 14. With such an arrangement, one or the other of the oppositely directed coupling elements 120 and 121 could be utilized to pull cars onto bridge 12 from either side of pit 4; however, since the coupling elements could not be revolved around to engage the opposite end of cars after they have been received onto track 14, the cars could only be pushed off of bridge 12 onto the same side of pit 4 from which they were received by utilizing the same coupling element that pulled them onto the bridge.

Various other changes and modifications in the con struction and arrangement of my railroad car classification apparatus may be utilized without departing from the spirit and scope of my invention as defined by the following claims.

I claim:

1. Railroad car handling and classification apparatus comprising:

an elongated pit in a railroad car yard;

a plurality of parallel, railroad car receiving, classification, and assembly tracks in said yard on oppo site sides of said pit and terminating at their inner ends at opposite side edges of said pit;

a movable bridge in said pit laterally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit so that said bridge extends substantially from one side edge to the other of said pit with sufficient clearance space at the opposite ends of said bridge to permit its movement;

power means drivingly associated with said bridge for moving said bridge back and forth in said pit;

a railroad car track on said bridge extending length wise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to and from said plurality of tracks;

a reversible continuous, endless belt type of car conveyor on said bridge looped around one of the two track rails forming the car track on said bridge, said car conveyor being looped in a horizontal plane about rotary guides located at opposite ends of said bridge, said guides having vertical axes and the top of said car conveyor being below the top of said car track on said bridge so that cars can pass over it;

two oppositely directed and oriented coupling'elements affixed to said car conveyor as parts of a single coupling assembly and constructed and arranged to be received in locking engagement with complementary couplings on opposite ends of a railroad car, said coupling elements being supported on said car conveyor at an elevation above said bridge track where they will be at the same level as said couplings on a railroad car, whereby said coupling elements can be moved with said car conveyor to a position between the rails of said bridge track for engagement with one of said car couplings, and whereby said coupling elements may be used to pull cars onto said bridge and push cars off of said bridge to and from siad tracks on both sides of said pit; and

power drive means on said bridge for moving said car conveyor in opposite directions.

2. Railroad car handling and classification apparatus as defined in claim 1 wherein:

said coupling elements are railroad car couplings operative for impact engagement and positive, interlocking connection with complementary couplings on railroad cars.

3. Railroad car handling and classification apparatus comprising:

an elongated pit in a railroad car yard;

a plurality of parallel, railroad car receiving, classification, and assembly tracks in said yard on opposite sides of said pit and terminating at their inner ends at opposite side edges of said pit;

a movable bridge in said pit laterally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit so that said bridge extends substantially from one side edge to the other of said pit with sufficient clearance space at the opposte ends of said bridge to permit its movement;

power means drivingly associated with said bridge for moving said bridge back and forth in said pit; railroad car track on said bridge extending lengthwise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to and from said plurality of tracks;

a continuous, endless belt type of car conveyor on said bridge having at least two, oppositely directed and oriented coupling elements thereon constructed and arranged to be received in locking engagement with complementary coupling means on opposite ends of a railroad car, whereby one of said coupling elements may be used to engage a coupling means on one end of a railroad car and pull it onto said bridge from one side of said pit, and the other one of said coupling elements may be moved with said car conveyor into engagement with coupling means on the opposite end of the railroad car to push it off of said bridge onto one of said plurality of tracks on the other side of said pit; and wherein said car conveyor is looped around one of two track rails forming the railroad car track on said bridge, said car conveyor being looped in a horizontal plane about rotary guides located at opposite ends of said bridge, said guides having vertical axes, and the top of said car conveyor being below the top of said car track on said bridge so that cars can pass over it, and said coupling elements being supported on said car conveyor at an elevation above said bridge track where they will be at the same level as said coupling means on a railroad car, whereby said coupling elements can be rotated with said car conveyor to a position between the rails of said bridge track for engagement with one of said car coupling means;

power drive means on said bridge for moving said car conveyor in opposite directions;

a removable track segment in said one bridge track rail at each end thereof;

first motor means connected to each of said removable track segments and operative to move said track segments out of said bridge track rail;

a longitudinally shiftable track section in said on bridge track rail at each end extremely thereof immediately adjacent one of said removable track segments; and

second motor means connected to each of said shiftable track sections and operative to reciprocate said shiftable track section longitudinally of said bridge track, whereby each of said shiftable track sections may be alternately retracted into the space vacated by one of said removable track sections to provide a clearance space at one end or the other of said one bridge track rail to permit said coupling elements to be carried around the ends of said one track rail for proper positioning of said coupling elements with railroad car couplings.

4. Railroad car handling and classification apparatus as defined in claim 3, and further including:

automatic control means at each end of said bridge so that said bridge substantially spans the length of said pit from one side edge to the other with sufficient clearance space at the opposite ends of said bridge to permit its movement;

power means drivingly associated with said bridge for moving said bridge back and forth in said pit;

a railroad car track on said bridge extending lengthwise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to and from said plurality of tracks;

a continuous, endless conveyor on said bridge having at least one coupling element attached thereto at such an elevation and location as to be received in locking engagement with complementary coupling means on the end of a railroad car, said coupling element extending upwardly above said railroad car track on said bridge, and the top of said car conveyor being below the top of said railroad car track on said bridge sothat cars can pass over it;

a pair of rotary guides having vertical axes located at opposite ends of said bridge about which said car conveyor is looped in a horizontal plane around one of two track rails forming said railroad car track on said bridge, whereby said coupling element can be rotated with said car conveyor to a position between said two rails of said bridge track for engagement with coupling means on a railroad car, said coupling element being so constructed and arranged on said car conveyor as to be movable therewith to a position wherein said coupling element is immediately adjacent one of the opposed side edges of said pit for releasing or picking-up a railroad car on one of said plurality of tracks;

displaceable track segments at both end extremities of one rail of said car track on said bridge, said track segments being displaceable to a position providing a clearance space at one end or the other of said one bridge track rail to permit said coupling element to be carried around the ends of said one track rail to a position wherein it is outside of said track on said bridge where it will not interfere with the movement of cars, across said bridge track from one side of said pit to the other; and

power drive means on said bridge for moving said car conveyor in opposite directions.

6. Railroad car handling and classification apparatus operative to sequentially actuate one of said first motor means to displace one of said removable track segments and then one of said second motor comprising:

an elongated pit in a railroad car yard; a plurality of parallel, railroad car receiving, classification, and assembly tracks in said yard on opposite sides of said pit and terminating at their inner ends at opposite side edges of said pit;

a movable bridge in said pit laterally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit so that said bridge extends substantially from one cation and assembly tracks in said yard on opposite sides of said pit and terminating at their inner ends at opposite side edges of said pit;

a movable bridge in said pit laterally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit side edge to the other of said pit with sufficient clearance space at the opposite ends of said bridge to permit its movement;

power means drivingly associated with said bridge for moving said bridge back and forth in said pit;

a railroad car track on said bridge extending lengthwise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to on one of said plurality of tracks on either side of said pit by engagement with a complementary coupling on the end of a railroad car; and

to a level even with said complementary coupling means on a railroad car at a position with respect to said car track on said bridge in alignment with said complementary coupling means on a railroad and from said plurality of tracks; car on one of said plurality of tracks or on said a car conveyor on said bridge having at least two, opbridge track for engagement therewith.

positely directed and oriented coupling elements 9. Railroad car handling and classification apparatus thereon constructed and arranged to be received in as defined in claim 6 wherein:

positive, locking engagement with complementary said car conveyor is an endless conveyor looped in a coupling means on the opposite ends of a railroad 10 horizontal plane about rotary guides located at opcar, said car conveyor extending lengthwise of said posite ends of said bridge and rotatable about vertibridge parallel and adjacent to said car track on cal axes, said car conveyor extending around one said bridge over substantially the entire length or two track rails forming said railroad car track on thereof, and said coupling elements being of such said bridge and said car conveyor being below the a shape and extent, and so mounted on said car 5 top of said car track on said bridge so that cars can conveyor as to be movable therdwith to a location pass over it, and said coupling elements being supadjacent said bridge car track wherein one or the ported on said car conveyor at an elevation above other of said coupling elements is immediately adsaid bridge track where they will be at the same jacent to one or the other of the opposed side edges level as said coupling means on a railroad car and of said pit for releasing or picking-up a railroad car rotatable into alignment therewith for positive,

coupling engagement with one of said car coupling means, and said coupling elements being movable with said car conveyor to positions at one side of said railroad track on said bridge where they will not interfere with movement of cars over said bridge. 10. Railroad car handling and classification apparatus as defined in claim 9, and further including:

plings constructed and arranged on said car conveyor to mate and be received in locking engagement with the oppositely directed couplings on the opposite ends of a railroad car normally used for coupling one car to another or to a switch engine.

displaceable track segments at both end extremities of said one rail of said car track on said bridge, said track segments being displaceable to a position providing a clearance space at one end or the other of said one bridge track rail to permit said coupling elements to be carried around the ends of said one track rail to a position wherein they are outside of said track on said bridge where they will not inter- 8. Railroad car handling and classification apparatus as defined in claim 7 wherein:

said coupling elements are parts of a single coupling assembly affixed to said car conveyor in such a manner that said coupling elements project upwardly above said railroad car track on said bridge fere with the movement of a car across said bridge track from one side of said pit to the other. 

1. Railroad car handling and classification apparatus comprising: an elongated pit in a railroad car yard; a plurality of parallel, railroad car receiving, classification, and assembly tracks in said yard on opposite sides of said pit and terminating at their inner ends at opposite side edges of said pit; a movable bridge in said pit laTerally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit so that said bridge extends substantially from one side edge to the other of said pit with sufficient clearance space at the opposite ends of said bridge to permit its movement; power means drivingly associated with said bridge for moving said bridge back and forth in said pit; a railroad car track on said bridge extending lengthwise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to and from said plurality of tracks; a reversible continuous, endless belt type of car conveyor on said bridge looped around one of the two track rails forming the car track on said bridge, said car conveyor being looped in a horizontal plane about rotary guides located at opposite ends of said bridge, said guides having vertical axes and the top of said car conveyor being below the top of said car track on said bridge so that cars can pass over it; two oppositely directed and oriented coupling elements affixed to said car conveyor as parts of a single coupling assembly and constructed and arranged to be received in locking engagement with complementary couplings on opposite ends of a railroad car, said coupling elements being supported on said car conveyor at an elevation above said bridge track where they will be at the same level as said couplings on a railroad car, whereby said coupling elements can be moved with said car conveyor to a position between the rails of said bridge track for engagement with one of said car couplings, and whereby said coupling elements may be used to pull cars onto said bridge and push cars off of said bridge to and from siad tracks on both sides of said pit; and power drive means on said bridge for moving said car conveyor in opposite directions.
 2. Railroad car handling and classification apparatus as defined in claim 1 wherein: said coupling elements are railroad car couplings operative for impact engagement and positive, interlocking connection with complementary couplings on railroad cars.
 3. Railroad car handling and classification apparatus comprising: an elongated pit in a railroad car yard; a plurality of parallel, railroad car receiving, classification, and assembly tracks in said yard on opposite sides of said pit and terminating at their inner ends at opposite side edges of said pit; a movable bridge in said pit laterally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit so that said bridge extends substantially from one side edge to the other of said pit with sufficient clearance space at the opposte ends of said bridge to permit its movement; power means drivingly associated with said bridge for moving said bridge back and forth in said pit; a railroad car track on said bridge extending lengthwise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to and from said plurality of tracks; a continuous, endless belt type of car conveyor on said bridge having at least two, oppositely directed and oriented coupling elements thereon constructed and arranged to be received in locking engagement with complementary coupling means on opposite ends of a railroad car, whereby one of said coupling elements may be used to engage a coupling means on one end of a railroad car and pull it onto said bridge from one side of said pit, and the other one of said coupling elements may be mOved with said car conveyor into engagement with coupling means on the opposite end of the railroad car to push it off of said bridge onto one of said plurality of tracks on the other side of said pit; and wherein said car conveyor is looped around one of two track rails forming the railroad car track on said bridge, said car conveyor being looped in a horizontal plane about rotary guides located at opposite ends of said bridge, said guides having vertical axes, and the top of said car conveyor being below the top of said car track on said bridge so that cars can pass over it, and said coupling elements being supported on said car conveyor at an elevation above said bridge track where they will be at the same level as said coupling means on a railroad car, whereby said coupling elements can be rotated with said car conveyor to a position between the rails of said bridge track for engagement with one of said car coupling means; power drive means on said bridge for moving said car conveyor in opposite directions; a removable track segment in said one bridge track rail at each end thereof; first motor means connected to each of said removable track segments and operative to move said track segments out of said bridge track rail; a longitudinally shiftable track section in said on bridge track rail at each end extremely thereof immediately adjacent one of said removable track segments; and second motor means connected to each of said shiftable track sections and operative to reciprocate said shiftable track section longitudinally of said bridge track, whereby each of said shiftable track sections may be alternately retracted into the space vacated by one of said removable track sections to provide a clearance space at one end or the other of said one bridge track rail to permit said coupling elements to be carried around the ends of said one track rail for proper positioning of said coupling elements with railroad car couplings.
 4. Railroad car handling and classification apparatus as defined in claim 3, and further including: automatic control means at each end of said bridge operative to sequentially actuate one of said first motor means to displace one of said removable track segments and then one of said second motor means to retract the adjacent one of said shiftable track sections in response to the proximity of one of said coupling elements to one end or the other of said one bridge track rail.
 5. Railroad car handling and classification apparatus comprising: an elongated pit in a railroad car yard; a plurality of parallel, railroad car receiving, classification and assembly tracks in said yard on opposite sides of said pit and terminating at their inner ends at opposite side edges of said pit; a movable bridge in said pit laterally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit so that said bridge substantially spans the length of said pit from one side edge to the other with sufficient clearance space at the opposite ends of said bridge to permit its movement; power means drivingly associated with said bridge for moving said bridge back and forth in said pit; a railroad car track on said bridge extending lengthwise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to and from said plurality of tracks; a continuous, endless conveyor on said bridge having at least one coupling element attached thereto at such an elevation and location as to be received in locking engagement with complementary coupling means on the end of a railroad car, said coupling element extending upwardly above said railroad car track on said bridge, and the top of said car conveyor being below The top of said railroad car track on said bridge so that cars can pass over it; a pair of rotary guides having vertical axes located at opposite ends of said bridge about which said car conveyor is looped in a horizontal plane around one of two track rails forming said railroad car track on said bridge, whereby said coupling element can be rotated with said car conveyor to a position between said two rails of said bridge track for engagement with coupling means on a railroad car, said coupling element being so constructed and arranged on said car conveyor as to be movable therewith to a position wherein said coupling element is immediately adjacent one of the opposed side edges of said pit for releasing or picking-up a railroad car on one of said plurality of tracks; displaceable track segments at both end extremities of one rail of said car track on said bridge, said track segments being displaceable to a position providing a clearance space at one end or the other of said one bridge track rail to permit said coupling element to be carried around the ends of said one track rail to a position wherein it is outside of said track on said bridge where it will not interfere with the movement of cars, across said bridge track from one side of said pit to the other; and power drive means on said bridge for moving said car conveyor in opposite directions.
 6. Railroad car handling and classification apparatus comprising: an elongated pit in a railroad car yard; a plurality of parallel, railroad car receiving, classification, and assembly tracks in said yard on opposite sides of said pit and terminating at their inner ends at opposite side edges of said pit; a movable bridge in said pit laterally shiftable in a direction transverse to said tracks, the length of said bridge in a direction parallel to said tracks being substantially coextensive with the length of said pit so that said bridge extends substantially from one side edge to the other of said pit with sufficient clearance space at the opposite ends of said bridge to permit its movement; power means drivingly associated with said bridge for moving said bridge back and forth in said pit; a railroad car track on said bridge extending lengthwise thereof over substantially the entire length of said bridge in a direction parallel to said plurality of tracks, said track on said bridge and said plurality of tracks being at the same elevation to permit railroad cars to be moved on and off said bridge to and from said plurality of tracks; a car conveyor on said bridge having at least two, oppositely directed and oriented coupling elements thereon constructed and arranged to be received in positive, locking engagement with complementary coupling means on the opposite ends of a railroad car, said car conveyor extending lengthwise of said bridge parallel and adjacent to said car track on said bridge over substantially the entire length thereof, and said coupling elements being of such a shape and extent, and so mounted on said car conveyor as to be movable therdwith to a location adjacent said bridge car track wherein one or the other of said coupling elements is immediately adjacent to one or the other of the opposed side edges of said pit for releasing or picking-up a railroad car on one of said plurality of tracks on either side of said pit by engagement with a complementary coupling on the end of a railroad car; and power drive means on said bridge for moving said car conveyor in opposite directions on said bridge.
 7. Railroad car handling and classification apparatus as defined in claim 6 wherein: said coupling elements are impact engagement couplings constructed and arranged on said car conveyor to mate and be received in locking engagement with the oppositely directed couplings on the opposite ends of a railroad car normally used for coupling one car to another or to a switch engine.
 8. Railroad car handling and classification apparatus as defined in claim 7 wherein: said coupling elements are parts of a single coupling assembly affixed to said car conveyor in such a manner that said coupling elements project upwardly above said railroad car track on said bridge to a level even with said complementary coupling means on a railroad car at a position with respect to said car track on said bridge in alignment with said complementary coupling means on a railroad car on one of said plurality of tracks or on said bridge track for engagement therewith.
 9. Railroad car handling and classification apparatus as defined in claim 6 wherein: said car conveyor is an endless conveyor looped in a horizontal plane about rotary guides located at opposite ends of said bridge and rotatable about vertical axes, said car conveyor extending around one or two track rails forming said railroad car track on said bridge and said car conveyor being below the top of said car track on said bridge so that cars can pass over it, and said coupling elements being supported on said car conveyor at an elevation above said bridge track where they will be at the same level as said coupling means on a railroad car and rotatable into alignment therewith for positive, coupling engagement with one of said car coupling means, and said coupling elements being movable with said car conveyor to positions at one side of said railroad track on said bridge where they will not interfere with movement of cars over said bridge.
 10. Railroad car handling and classification apparatus as defined in claim 9, and further including: displaceable track segments at both end extremities of said one rail of said car track on said bridge, said track segments being displaceable to a position providing a clearance space at one end or the other of said one bridge track rail to permit said coupling elements to be carried around the ends of said one track rail to a position wherein they are outside of said track on said bridge where they will not interfere with the movement of a car across said bridge track from one side of said pit to the other. 